Computer networks allow multiple computers, peripherals and other information storage, retrieval or processing devices to share data. Each device attached to a network is typically referred to as a node on the network, or a node that is part of the network. Local Area Networks (“LANs”) have historically consisted of nodes interconnected by physical telecommunications media (e.g., coaxial cable, twisted pair wire, or fiber optics). Recently wireless LANs, the nodes of which are not connected by means of a physical medium, have started to appear in the market. These wireless LANs communicate by means of infra-red (IR), radio or other signals. One of the benefits of using wireless LANs is that cabling is not required. This is a particularly useful feature for mobile nodes such as laptop and notebook computers, PDAs (personal digital assistants), and the like. If appropriately equipped with an appropriate wireless adapter, the mobile nodes can move around within a predefined coverage area and remain connected to the network.
Certain wireless LANs are implemented similarly to cellular telephone networks. In such implementations the wireless mobile nodes of the LAN do not communicate directly with each other, but rather send all signals to a central base station for redirection to a destination node. A similar arrangement is contemplated for the proposed “Bluetooth” wireless communications protocol. This protocol is predicated on the grouping of physically proximate wireless nodes into “piconets”, and is described in Specification of the Bluetooth System, v0.8, Jan. 22, 1999 (and in subsequent revisions thereof).
In the Bluetooth system each piconet includes a master unit and at least one slave unit. The Bluetooth protocol specifies a time-division duplex communication scheme in which each slave unit is polled by the master unit immediately prior to transmitting information. Once polled, the addressed slave unit transmits during the next time slot. Since each time slot is specified to be 625 microseconds in length, no members of the piconet other than the master unit and the addressed slave unit are able to transmit during the 1,250 microsecond duration of this exchange. The Bluetooth protocol currently allows for 7 active slave units within a given piconet, with each slave unit being given the opportunity to transmit information on average every 14 slots. Since a single slot may contain up to 18 user data bytes, each slave unit may transmit at up to 16 kb/second. Unfortunately, if all slave units require less than this amount of bandwidth, the difference is wasted unless additional slave units are “parked” and “unparked” pursuant to the Bluetooth protocol. However, a significant amount of overhead is associated with this “parking” mechanism, and its use may result in potentially long idle periods preceding transmission from newly “unparked” slave units.
Accordingly, it would be desirable to enable relatively larger numbers of slave units to simultaneously participate in Bluetooth and other networks in a manner avoiding the inefficiencies described above.